1. Field of the Invention
This invention relates to a new class of linear nitrogen heterocycle-containing copolymers and especially to those elastomers composed of block copolymers having alternating "soft" and "hard" segments in their internal structure with the "hard" segment being derived from a polymer having a majority of isocyanurate groups.
2. Description of the Prior Art
Isocyanurate compositions, such as those described in U.S. Pat. No. 3,407,200, are known as intermediates for the preparation of a variety of synthetic polymers useful as fibers, filaments, and the like. The materials prepared from such isocyanurate compositions exhibit excellent properties such as strength and elasticity, which is valuable in the manufacture of various protective coatings, as well as rope, hawser, fishing line, and so forth.
It is well known that physical blends of chemically dissimilar polymers are incompatible, and when blended in an attempt to modify their properties, suffer a substantial phase separation (and a lack of clarity) as well as the general degradation of the mechanical properties. Improvements over the physically blended polymers have been obtained by random copolymerization of desired prepolymeric materials. Recently, it has been noted that further improvements over the random copolymers are obtained by introducing a certain degree of order into the polymeric chain. One method to accomplish such improvement is by the formation of block copolymers. These materials are primarily defined as polymeric chains comprising two or more polymer segments of different chemical composition attached end to end. The term block copolymer can also include copolymers where very short polymer segments are attached together. As a limiting case, a regularly alternating copolymer may also be considered as block copolymer. Block copolymers may also include those segments formed from polar and nonpolar, crystalline and amorphous, and elastomeric and nonelastomeric structures. In block copolymers of the thermoplastic elastomeric type, the copolymer comprises amorphous segments having a low T.sub.g, e.g., "soft" segments, and segments of high T.sub. g, e.g., "hard" segments. Of particular interest are those block copolymers which have as hard segments polymeric chains containing a majority of polyisocyanurate linkages.